1. Field of the Invention
The present invention relates to an apparatus and method for mainstream patient airway medical monitoring, such as by using a capnometer.
2. Description of Related Art
The measurement of carbon dioxide levels in respiration is a standard procedure during intensive care and anesthesia and is a primary tool in the diagnosis and management of respiratory function. A need in this medical monitoring is to measure and track CO2 concentration in the breath, sometimes referred to as capnography.
To meet the necessary specifications of such capnography device, current technology relies on bulky and expensive non-dispersive infrared absorption (NDIR) sensors to determine CO2 concentration. The high cost and limitations of this technology restrict the use of capnography to high value, controlled environments, such as surgical wards. In addition, it has been shown that capnography is particularly important in determining the proper placement of endotracheal tubes in emergency medical response.
There are two approaches to implement this detection method, mainstream and sidestream. Mainstream devices make use of a sensor located at the patient airway by means of an airway adapter. In contrast, sidestream device requires connection of a sample line to the airway, and a sensor located away from the patient. Notwithstanding the advantages of these approaches, each may be subject to certain limitations that may compromise the effectiveness of CO2 monitoring.
A comparison of exemplary limitations of prior-art apparatus and methods are listed below:
Mainstream                Secretions and humidity block the sensor.        A heating element is used to negate condensation.        A bulky device is at the patient airway.        The sensor must be sterilized and calibrated after each use.        The sensor is not usable with non-intubated patients.        
Sidestream                Secretions block sample tubing.        A necessity for a water trap.        A slower response for CO2 changes.        Reduced air flow decreases tidal volume.        Additional sample tubing.        A costly pump and suction system.        
It is desirable, therefore, to provide an apparatus and method for monitoring CO2 or other gases in a patient's airway, that overcomes the limitations of the prior art.